I think it's reasonable. Not the exact details of this installation necessarily. The reality is that there are a bunch of people that want to lash out at the government for whatever reason, and the civil servants that just want to do their job shouldn't be put in a dangerous situation by allowing those people to walk into their offices unimpeded. If you believe that the agency shouldn't exist, lobby Congress. Don't take it out on people that just want to do their assigned administrative work for 8 hours a day.

Remember that someone was so mad at the IRS that they filled their airplane with gas cans and flew it into an IRS building, killing an employee: https://en.wikipedia.org/wiki/2010_Austin_suicide_attack

Some security precautions are understandable in my opinion. (I don't think the ID requirement is reasonable. Take and store a photograph, deleted after 3 months, and make people go through a metal detector. Also, put the ID requirement documents online. It's free.)

There's also been significantly worse. 168 people died in the Oklahoma City bombing by a domestic terrorist. https://en.wikipedia.org/wiki/Oklahoma_City_bombing